Giant Pokémon

Giant Pokémon, while rarely playing a large part in terms of plot, are nonetheless a recurring theme in the Pokémon anime. There are several episodes that have a plot revolving around unusually large Pokémon, such to the point that it seems to be a rather common mutation for Pokémon to go through.

Ancient giant Pokémon

Several ancient giant Pokémon appeared in the The Ancient Puzzle of Pokémopolis. These Pokémon were all covered in tattoo-like marks. Gengar emerged from a black vajra-like artifact, Alakazam emerged from a spoon-like artifact, and Jigglypuff emerged from an ancient bell.

In the games

In Hey You, Pikachu! one of the activities involves Pikachufishing, and it is possible to fish Pokémon much larger than average. There is also an Oddish that, instead of evolving, grows larger when it is watered, until it is at least ten times Pikachu's size.

In the Super Smash Bros. series, the player can be temporarily large by eating the Super Mushroom. Jigglypuff's Final Smash, Puff Up can make Jigglypuff gigantic temporarily, plus knocking out any opponent near it.